U.S. Pat. No. 4,400,340 and U.S. Pat. No. 4,426,502 disclose the production of a molded article by injecting a reactive liquid mixture comprising norbornene-type monomer such as dicyclopentadiene (called "DCP" hereinafter) and a metathesis polymerization catalyst system into a mold in which said liquid mixture is metathesis polymerized in bulk (called "RIM process" hereinafter). RIM process is a low pressure one step or one-shot injection of a liquid mixture into a closed mold where rapid polymerization occurs resulting in a molded article. Thus, there are easily produced large-sized molded articles from DCP and the like by RIM process. The molded articles have been taken notice from the industrial point of view since they have attractive physical properties as balanced in stiffness and impact resistance. However, the molded articles produced from DCP by said RIM process have low softening points generally below 120.degree. C., and this often limits the use of the molded articles produced from DCP, etc.
Further, the metathesis polymerization catalyst system used in RIM process comprises a catalyst component comprising a compound of a transition metal such as tungsten, molybdenum, rhenium or tantalium and an activator component comprising an organic metal compound of aluminum, tin or the like. The metathesis polymerization catalyst system initiates the polymerization reaction upon mixing of the catalyst component and the activator component. RIM process utilizes advantageously characteristics of the metathesis polymerization catalyst system, and therein there is produced a molded article by mixing the first reactive solution containing the catalyst component and a monomer such as DCP and the second reactive solution containing the activator component and the monomer and then immediately injecting the mixture into a mold.
However, both of the catalyst component and the activator component of said catalyst system are too active for polymerizing a cycloolefin such as DCP in bulk even at room temperature, and thus the polymerization of DCP and the like often occurs before poured into a mold, and it makes the pouring of the mixture into the mold difficult.
Therefore, it is desirable to moderate the metathesis polymerization reaction as to provide an adequate induction period.
Said U.S. Pat. No. 4,400,340 discloses using Lewis-bases to moderate the polymerization reaction of RIM process. However, Lewis-bases remaining in the polymer injure molded polymer articles and often produce undesired volatile compounds.
Said U.S. Pat. No. 4,426,502 is characterized by the use of a particular metathesis polymerization catalyst system to moderate the polymerization reaction of RIM process. However, this requires the inconvenient limited selection of the metathesis polymerization catalyst system.
Recently, there has been produced a molded article by so-called "pre-mix process" which comprises mixing a metathesis polymerization catalyst system and a monomer such as DCP to prepare a pre-mixture with a static mixer and the like instead of a impingement mixer in case of RIM and then introducing the pre-mixture into a mold.
A molded article can be produced more easily by pre-mix process than by RIM process, since pre-mix process requires simpler molding devices than in RIM process. However, pre-mix process necessitates the more effective moderation of the metathesis polymerization reaction than RIM process.
Further, Japanese Patent Laid Open Sho 61-179214 discloses that there are produced copolymers having relatively high glass transition temperatures by the metathesis copolymerization of norbornene-type cycloolefins such as DCP with other metathesis polymerizable norbornene-type comonomers having a polar group on 5-position of norbornene-moiety and that said other metathesis polymerizable comonomers can moderate the metathesis polymerization reaction.
The above Japanese patent publication discloses that some of carboxylic acid esters containing two norbornene-moieties can be used as a comonomer with DCP. The esters disclosed therein are those of which two mono-carboxylic acid residues have individually one norbornene-moiety but the glycol residue does not have the norbornene-moiety, such as ethylene bis(5-norbornenylcarboxylate), or those of which two mono-alcohol residues have individually one norbornene-moiety but the dicarboxylic acid residue does not have the norbornene-moiety, such as bis(5-norbornenyl-methyl)phthalate.
In said Japanese patent publication, however, it is rather difficult to obtain said esters in a pure form because of rather high molecular weight of the esters. Further, the attained increase of glass transition temperature of the polymers is at most about 50.degree. C. and is not enough.
Now, we have found that particular metathesis polymerizable carboxylic acid esters of which the acid residue and alcohol residue have individually at least one norbornene-moiety are easy to prepare and can moderate very effectively the metathesis polymerization reaction of DCP and the like. Thus, it is very advantageous to use said carboxylic acid esters in the above mentioned RIM-process and pre-mix process.
Further, we have found that there can be produced highly cross-linked heat resistant copolymers having a very high softening point by copolymerization of the metathesis polymerizable cycloolefins such as DCP with the metathesis polymerizable carboxylic acid esters.
Therefore, it is an object of the present invention to provide cross-linked heat resistant metathesis polymerized copolymers having a very high softening point.
A further object of the present invention is to provide a process for producing said copolymers under a moderated reaction condition.
Another objects of the present invention is to provide a process for producing molded articles comprising the copolymers. A further object of the present invention is to provide polymerizable composition used for producing said copolymers and molded articles. Another object is to provide molded articles.